Conversions fuels, heating values

Figure 8.1 is based on field-erected cost for furnaces designed to elevate hydrocarbon streams to 700°F at 500 psi (maximum) with absorbed heat duties in excess of 10 mmBtu/h. All tube banks are carbon steel, except pyrolysis or reformer furnaces, which have stainless tubes. Process furnaces generally have overall fuel efficiency of 75% (lower fuel heating value conversion to actual absorbed heat). Although most furnace vendors claim much higher efficiencies, this 75% efficiency value is... 

Coal Char This type of char is the nonagglomerated, nonfusible residue from the thermal treatment of coal. Coal chars are obtained as a residue or a coproduct from low-temperature carbonization processes and from processes being developed to convert coal to hquid and gaseous fuels and to chemicals. Such chars have a substantial heating value. The net amount of char from a conversion process varies widely in some instances, it may represent between about 30... 

The mass and heat balances of the process are satisfactory when coal is gasified to a 53% carbon conversion in the gasifier and the remaining 47% of carbon is sent to the regenerator. From the heat values of the produced fuel gas and the input coal, the cold-gas efficiency (91 vol% H2 with 9 vol% CH4 298 K, 0.1 MPa) was calculated to be higher than 0.77. 

Heat recovery efficiency is a consideration of major importance in the conversion of coal to secondary fuels. This parameter is defined as the percent of the heating value of the coal used which is recovered as heating value in the desired secondary fuel. Heat recovery efficiency which can be attained in a coal conversion process depends firstly on the theoretical chemical and thermodynamic requirements of the process, and secondly on the practical realization of the process. The first factor determines the theoretical maximum heat recovery efficiency that can be obtained under ideal circumstances. The second factor determines the extent to which the practical process approaches the theoretical ideal. 

Cold gas conversion efficiency is the ratio of the gasifier fuel gas total heating value [i.e., (heating value)(mass flow)] to that of the coal feed, [(heating value)(mass flow)]. 

An alternative approach for the utilization of biomass resources for energy applications is the production of dean-buming liquid fuels. In this respect, current technologies to produce liquid fuels from biomass are typically multi-step and energy-intensive processes. Aqueous phase reforming of sorbitol can be tailored to produce selectively a clean stream of heavier alkanes consisting primarily of butane, pentane and hexane. The conversion of sorbitol to alkanes plus CO2 and water is an exothermic process that retains approximately 95% of the heating value and only 30% of the mass of the biomass-derived reactant [278]. 

With the conversion to a mechanical feed system, they expect to double their tdf feed capacity and run 4 tons per hour. This should result in a considerable fuel cost savings, because they can obtain tdf for about 1 per million Btu, whereas they would otherwise be burning more coal which costs about 2 per million Btu. With the new configuration they could obtain 10 percent of their heating value from tdf, 10 percent from natural gas, and 80 percent from coal. Both their old and new configurations utilize 2-inch by 2-inch pieces of tdf. With the new capacity Arizona Portland could increase its capacity to over 3 million scrap tires per year. In 1990, Arizona Portland utilized approximately 1 million scrap tires (54). 

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